Fine Control over the Compositional Structure of Trimetallic Core-Shell Nanocrystals for Enhanced Electrocatalysis

Directing Energy Flow in Core-Shell Nanostructures for Efficient Plasmon-Enhanced Electrocatalysis

Conjugating plasmonic metals with catalytically active materials with controlled configurations can harness their light energy harvesting ability in catalysis. Herein, we present a well-defined core-shell nanostructure composed of an octahedral Au nanocrystal core and a PdPt alloy shell as a bifunctional energy conversion platform for plasmon-enhanced electrocatalysis. The prepared Au@PdPt core-shell nanostructures exhibited significant enhancements in electrocatalytic activity for methanol oxidation and oxygen reduction reactions under visible-light irradiation. Our experimental and computational studies revealed that the electronic hybridization of Pd and Pt allows the alloy material to have a large imaginary dielectric function, which can efficiently induce the shell-biased distribution of plasmon energy upon illumination and, hence, its relaxation at the catalytically active region to promote electrocatalysis.

Fermi Level Equilibration at the Metal-Molecule Interface in Plasmonic Systems

We highlight a new metal-molecule charge transfer process by tuning the Fermi energy of plasmonic silver nanoparticles (AgNPs) in situ. The strong adsorption of halide ions upshifts the Fermi level of AgNPs by up to ∼0.3 eV in the order Cl^- < Br^- < I^-, favoring the spontaneous charge transfer to aligned molecular acceptor orbitals until charge neutrality across the interface is achieved. By carefully quantifying, experimentally and theoretically, the Fermi level upshift, we show for the first time that this effect is comparable in energy to different plasmonic effects such as the plasmoelectric effect or hot-carriers production. Moreover, by monitoring in situ the adsorption dynamic of halide ions in different AgNP-molecule systems, we show for the first time that the catalytic role of halide ions in plasmonic nanostructures depends on the surface affinity of halide ions compared to that of the target molecule.

Solvent-Mediated Shell Dimension Reconstruction of Core@Shell PdAu@Pd Nanocrystals for Robust C1 and C2 Alcohol Electrocatalysis

The core@shell structure dimension of the Pd-based nanocrystals deeply impacts their catalytic properties for C1 and C2 alcohol oxidation reactions. However, the precise simultaneous control on the synthesis of core@shell nanocrystals with different shell dimensions is difficult, and most synthesis on Pd-based core@shell nanocatalysts involves the surfactants participation by multiple steps, thus leads to limited catalytic properties. Herein, for the first time, a facile one-step surfactant-free strategy is developed for shell dimension reconstruction of PdAu@Pd core@shell nanocrystals by altering volume ratios of mixed solvents. The Pd-based sunflower-like (SL) and coral grass-like (CGL) nanocrystals are obtained with different 2D hexagonal nanosheet assembles and 3D network shells, respectively. Benefitting from the clean surface shell of 2D ultrathin nanosheets structure, high atom utilization efficiency, and robust electronic effect. The PdAu@Pd SL achieves the ascendant methanol/ethanol/ethylene glycol oxidation reaction (MOR/EOR/EGOR) activities, much higher than Pd/C catalysts, as well as the improved antipoisoning ability. Notably, this one-step construction shell dimension of PdAu@Pd core@shell catalysts not only provide a significant reference for the improvement of surfactant-free synthetic routes, but also shed light on the advanced engineering on shell dimensions in core@shell nanostructures for electrocatalysis and so forth.

A review of the role and mechanism of surfactants in the morphology control of metal nanoparticles

Although great progress has been made in the synthesis of metal nanoparticles, good repeatability and accurate predictability are still difficult to achieve. This difficulty can be attributed to the synthetic method based primarily on observation and subjective experience, and the role of many surfactants remains unclear. It should be noted that surfactants play an important role in the synthetic process. Understanding their function and mechanism in the synthetic process is a prerequisite for the rational design of nanocatalysts with ideal morphology and performance. In this review article, the function of surfactants is introduced first, and then the mechanism of action of surfactants in controlling the morphology of nanoparticles is discussed according to the types of surfactants, and the promoting and sealing effects of surfactants on the crystal surface is revealed. The relationship between surfactants and the morphology structure of nanoparticles is studied. The removal methods of surfactants are discussed, and the existing problems in the current development strategy are summarized. Finally, the application of surfactants in controlling the morphology of metal nanocrystals is prospected. It is hoped that the review can open up new avenues for the synthesis of nanocrystals.

Flexible synthesis of Au@Pd core-shell mesoporous nanoflowers for efficient methanol oxidation

The design of bimetallic core-shell nanostructures with mesoporous surfaces is considered significant to strengthen the catalytic activity and stability for direct methanol fuel cells. Here, we report a flexible method to synthesize Au@Pd core-shell mesoporous nanoflowers (Au@mPd NFs) with Au core coated with mesoporous Pd nano-petals, in which polymeric micelle-assembled structures are used as templates to induce the formation of mesopores. Benefiting from the electronic and structural effects, Au@mPd NFs show excellent electrocatalytic activity and stability for methanol oxidation reaction in alkaline electrolytes. This study demonstrates a versatile strategy for the fabrication of core-shell mesoporous nanoflowers with adjustable composition.

Enriching the branching of Au@PdAu core–shell nanocrystals using a syringe pump: kinetics control meets lattice mismatch

Gold@palladium–gold nanocrystals with a tunable branched shape are prepared via seeded growth, where the use of a syringe pump allows the manipulation over reaction kinetics as coupled by surface diffusion and strain caused by lattice mismatch.